1.3- Diols 1,3-cyclobutanediols

Neopentyl glycol adipate Cyclohexane dimethanol adipate Tetramethyl cyclobutanediol adipate Neopentyl glycol succinate Butane-1,4-diol succinate Phenyl diethanolamine succinate Ethylene glycol sebacate Neopentyl glycol sebacate Ethylene glycol isophthalate Ethylene glycol phthalate... 

In the case of 1-alkylated 1,2-cyclobutanediols, the tertiary hydroxyl is the preferred or exclusive leaving group. With 1,2-dialkylated diols, the trans isomers were normally found to rearrange somewhat more easily than the cis compounds. For instance, trans-1,2-dimethyl-l,2-cyclobutanediol (243) underwent immediate quantitative ring contraction to (1-methylcyclopropyl) methyl ketone (244) upon treatment with boron trifluoride etherate at room temperature while the ring contraction of the cis isomer (245) was observed only on heating at 70°C for 5 min in the presence of BF3 and Et20 (equation 166) . 

The 1,2-cyclobutanediols also undergo thermal rearrangement. The reaction is performed in high yields either in a sealed tube at 230-270°C or in the gas phase. The simple mono- and dialkylated compounds give products which are the same as those formed in the acid-catalysed reaction, and the tram diols were found to rearrange faster than their cis counterparts (equation 166) . 

After the butyl alcohol was removed, the polymers were built up by heating the melt under reduced pressure. Since these polyformals of aliphatic diols had very low melting points (below 75° C.), their utility was limited. Apparently, no higher melting points have been reported for polyformals. In attempts to obtain higher-melting polyformals, the following alicyclic diols were used cis-, trans-, and 1 to 1 cis-/trans- mixture of 2,2,4,4-tetramethyl-l,3-cyclobutanediol (I) trans-1,4-cyclohexanediol (II) tmiw-l,4-cyclohexanedimethanol (III) and 2,5- or 2,6-norbomanediol (IV). 

Materials. 2,2,4,4-Tetramethyl-1,3-cyclobutanediol. The diol was a commercial product (Tennessee Eastman Co.). Unless otherwise indicated, the diol consisted of a cis-/trans- mixture with about a 1 to 1 isomer ratio. The cis-isomer was obtained from the isomer mixture by transforming the trans- isomer into an unsaturated aldehyde with aqueous sulfuric acid (4). The mrw-diol was obtained by preparing the diformate of the isomer mixture, separating the trans-derivative from the cis- derivative by recrystallization, and converting the transdiformate to the diol by methanolysis (5). 

Paraformaldehyde Method. 2,2,4,4-Tetramethyl-1,3-cyclobutanediol. A 2-liter, three-necked flask was fitted with a glass stirrer, thermometer, and Dean-Stark trap which was filled with distilled cyclohexane and attached to a water-cooled condenser. In the flask were placed 216 grams (1.5 moles) of 2,2,4,4-tetramethyl-l,3-cyclobutanediol (1 to 1 cis-/trans- mixture), 52.2 grams (1.65 moles, if 95% pure) of paraformaldehyde, 1200 ml. of distilled cyclohexane, and 0.20 gram of methanedisulfonic acid in a 10 to 25% aqueous solution. (The catalyst solution had been treated with Darco G-60 to remove all color.) While this mixture was stirred at 60° C., the paraformaldehyde depolymerized to formaldehyde, which reacted with the diol. Complete reaction of these two components was indicated when they had gone into solution. This required about 1 hour. 

The solid-phase method of building up polyformals is applicable only to high-melting polymers. The required melting point is not known, but the poly-formal of trarw-l,4-cyclohexanediol melted at 206°—10° C. and that of the cis-/ trans- mixture of 2,2,4,4-tetramethyl-l,3-cyclobutanediol melted appreciably higher. The solution method did not appear to be applicable to building up the polyformals of these two diols, since inherent viscosities below 0.4 were obtained. The solution method may be most applicable to primary diols, such as cyclohexanedimethanol and decanediol, which gave polyformals with inherent viscosities of 0.9. 

Bour, C. and Suffert, J. (2006) 4-exo-dig cyclocarbopalladation a straightforward synthesis of cyclobutanediols from acyclic y-bromopropargyhc diols under microwave irradiation conditions. Eur. J. Org. Chem., 1390-5. 

Another copolyester is prepared from two diols, CHDM and 2,4,4-tetramethyl-l,3-cyclobutanediol (TMCD). These diols, which have cis and trans con-hgurations, are reacted with dimethyl terephthalate to give an amorphous, transparent copolyester [36]. This amorphous copolyester features good chemical and heat resistance, which make this copolyester suitable for hot-fill cosmetics packaging, personal care and fragrance packaging. These polymers are available from Eastman Chemical under that Tritan trade name. The structure of CHDM/TMCD copolyester is depicted in Fig. 1.21. 

In 2006, Bout and Suffert combined Stille coupling with a preceding intramolecular alkyne insertion into a vinylic palladium bond and developed a new application of the 4-exo-dig cyclocarbopalladation of acyclic y-bromopropargylic diols 120 [48] (Scheme 6.30). This strategy is an efficient route to cyclobutanediol derivatives 121. The efficiency of the reaction is improved greatly by the use of brief microwave irradiation at 130 °C. Further 6ii-electrocyclization occurred, providing new bicyclic systems 123 instead of trienes 122, when the reaction was conducted in the presence... 

Polymerizations of 1 with 2,5-hexanediol and 1,3-cyclohexanediol afforded polymers 3 and 4, respectively. These polymers had molecular wdghts which were substantially lower than 2a-d. This is attributable to an elimination process involving the choroformate-pyridine complex as a side reaction, which becomes more important with the less reactive secondary diols (26), Daly reported polymerizations of cyclo-hexanediol with tetramethyl cyclobutanediol dichloroformate afforded high molecular weight polymer, this being a case where elimination cannot occur due to the metbyl substitution at the p- position (27). 

---